Induction heating device

ABSTRACT

The present invention offers an induction heating apparatus in which the infrared sensor performs stable temperature detection without undergoing the influence of leakage magnetic flux from the induction heating means. This induction heating apparatus has a main frame which forms an outer casing, a top plate provided on the upper side plane of the above-mentioned main frame and having at least one loading part on which a cooking container to be heated is placed, an induction heating means which is provided under the above-mentioned loading part and is to heat the above-mentioned cooking container to be heated, an infrared sensor which is provided in the neighborhood of the above-mentioned induction heating means and receives the infrared radiation radiated from the above-mentioned cooking container to be heated, and outputs the detected signal corresponding to the amount of the infrared radiation, a control board that detects the temperature of the above-mentioned cooking container to be heated based on the above-mentioned detected signal, and controls the output of the above-mentioned induction heating means, and a magneto-shielding member having a cylindrical body covering the periphery of the above-mentioned infrared sensor and a side part covering at least a part of the above-mentioned control board and being composed thereof in a single unitary body.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Section 371 of International Application No.PCT/JP2004/009702. filed Jul. 1, 2004, which was published in theJapanese language on Jan. 13, 2005, under International Publication No.WO 2005/004541 A1, the disclosure of which is incorporated herein byreference.

1. Technical Field

The present invention relates to induction heating apparatus equippedwith an infrared sensor.

2. Background Art

In recent years, as for the cooking apparatus without using fire, marketof induction heating apparatus has been growing. Referring to FIG. 5 andFIG. 6, induction heating apparatuses of prior art examples areelucidated. The induction heating apparatus of a prior art 1 isdescribed using FIG. 5. FIG. 5 is a cross-sectional drawing showing aconfiguration of an induction heating apparatus of the prior art 1 usinga thermo-sensitive element. The induction heating apparatus of prior art1 comprises a main frame 1 that forms an external casing, a top plate 2made of non-magnetic material and on which a cooking container 53 is tobe placed, an induction heating coil 4 which is arranged under the topplate 2 for induction-heating a cooking container 53, a thermo-sensitiveelement 54 that is made contacted with pressure to the back side of thetop plate 2 and outputs detected signal responding to the temperaturethereof, a temperature calculation means 51, and a control means 52. Inthe induction heating apparatus of the prior art 1, temperature of thebottom plane of a cooking container 53 placed on the top plate 2 isdetected using a thermo-sensitive element. The temperature calculationmeans 51 calculates the temperature of the cooking container 53 based onthe output signal of the thermo-sensitive element 54. The control means52 controls the electric power supplied to the induction heating coil 4based on the temperature information obtained from the temperaturecalculation means 51.

The control means 52 supplies a high frequency current to the inductionheating coil 4. The induction heating coil 4 generates a high frequencymagnetic field. This high frequency magnetic field crosses with thecooking container 53 and the cooking container 53 itself isinduction-heated and generates heat. Material to be cooked contained inthe cooking container 53 is heated by the heat generated in the cookingcontainer 53 and the cooking process proceeds. Based on the temperaturesignal that is detected by the temperature calculation means 51, thecontrol means 52 adjusts the electric power to be supplied to theinduction heating coil 4; by this electric power adjustment, thetemperature of the material to be cooked is controlled.

The thermo-sensitive element 54 detects the temperature of cookingcontainer 53 through the top plate 2. The top plate 2 is composed ofceramic and hence the thermal conductivity is small. Therefore, delayoccurred in the temperature detection of the cooking container 53 by thethermo-sensitive element 54, and there has been a problem that theconventional induction heating apparatus is inferior in the heatresponse characteristic.

The induction heating apparatus of a prior art 2 is described using FIG.6. FIG. 6 is a cross-sectional drawing showing the composition of aninduction heating apparatus of a prior art 2 in which an infrared sensoris used. In FIG. 6, the point that is different from that in FIG. 5 isthat it has an infrared sensor 5 in place of the thermo-sensitiveelement 54. Since the other components are identical with figure FIG. 5,identical numerals are used and explanations thereof are omitted.

An infrared sensor 5 is arranged under the top plate 2 and detects theinfrared radiation radiated from the bottom plane of the cookingcontainer 53 across the top plate 2; the infrared sensor 5 outputs asignal according to the temperature which is detected in this manner.Temperature calculation means 51 calculates the temperature of cookingcontainer 53 based on the output signal of the infrared sensor 5. Thecontrol means 52 controls a power supplied to the induction heating coil4 based on the information obtained from the temperature calculationmeans 51.

The infrared radiation radiated from the cooking container 53 passesthrough the top plate 2 and reaches the infrared sensor 5. In thetemperature detection system using the infrared sensor 5, the problemthat the inferiority in the heat response was conquered (Reference to,for example, Japanese Unexamined Patent Publication No. Hei 03-184295).

However, when the infrared sensor 5 is arranged in the neighborhood ofthe induction heating coil 4 as in the composition of the inductionheating apparatus of the prior art 2, the following problem occurs: Thatis, the infrared sensor undergoes influences of the induction magneticfield from the induction-heating coil 4, which was occurring during thecooking by the induction heating, thereby the infrared sensor 5 itselfgenerates the heat. As a result, in the conventional induction heatingapparatus, it was not possible to attain an accurate temperaturedetection, and hence the stable heating control could not be realized.

The present invention intends to dissolve the above-mentioned hithertoexisting problem: In the present invention, it purposes to provide theinduction heating apparatus in which an infrared sensor performs astable temperature detection without undergoing influences by the leakmagnetic flux from the induction heating means.

DISCLOSURE OF INVENTION

In order to dissolve the above-mentioned problem, the induction heatingapparatus according to the present invention has;

a main frame that forms an outer casing,

a top plate provided on the upper side plane of the above-mentioned mainframe and having at least one loading part on which a cooking containerto be heated is placed,

an induction heating means that is provided under the above-mentionedloading part and is to heat the above-mentioned cooking container to beheated,

an infrared sensor which is provided in the neighborhood of theabove-mentioned induction-heating means and receives the infraredradiation radiated from the above-mentioned cooking container to beheated, and outputs the detected signal corresponding to the amount ofradiation thereof,

a control board that detects the temperature of the above-mentionedcooking container to be heated based on the above-mentioned detectedsignal, and controls the output of the above-mentioned induction heatingmeans,

a magneto-shielding member configured in a single unit including acylindrical part which covers the periphery of the above-mentionedinfrared sensor and a side part which covers at least a part of theabove-mentioned control board.

The present invention has the technical effect that it can realize theinduction heating apparatus in which an infrared sensor detects stablythe temperature in high accuracy without undergoing influences by theleakage magnetic flux from the induction heating means.

While the novel features of the invention are set forth particularly inthe appended claims, the invention, both as to organization and content,will be better understood and appreciated, along with other objects andfeatures thereof, from the following detailed description taken inconjunction with the drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional drawing of principal part showing theconfiguration of the induction heating apparatus in an embodiment 1 ofthe present invention.

FIG. 2 is a cross-sectional drawing of principal part showing theconfiguration of the induction heating apparatus in an embodiment 2 ofthe present invention.

FIG. 3 is a cross-sectional drawing of principal part showing theconfiguration of the induction heating apparatus in an embodiment 3 ofthe present invention.

FIG. 4 is an exploded perspective view of the control unit of theembodiments 1 to 3 of the present invention.

FIG. 5 is a cross-sectional drawing showing the configuration of aninduction heating apparatus of prior art using a thermo-sensitiveelement.

FIG. 6 is a cross-sectional drawing showing the configuration of aninduction heating apparatus using an infrared sensor.

It will be recognized that some or all of the Figures are schematicrepresentations for purposes of illustration and do not necessarilydepict the actual relative sizes or locations of the elements shown.

BEST MODE FOR CARRYING OUT THE INVENTION

An induction heating apparatus according to one aspect of the presentinvention has;

a main frame that forms an outer casing,

a top plate provided on the upper side plane of the above-mentioned mainframe and having at least one loading part on which a cooking containerto be heated is placed,

an induction heating means, which is provided under the above-mentionedloading part and is to heat the above-mentioned cooking container to beheated,

an infrared sensor which is provided in the neighborhood of theabove-mentioned induction heating means and receives the infraredradiation radiated from the above-mentioned cooking container to beheated, and outputs the detected signal corresponding to the amount ofradiation thereof,

a control board that detects the temperature of the above-mentionedcooking container to be heated based on the above-mentioned detectedsignal, and controls the output of the above-mentioned induction heatingmeans,

a magnetic shielding member configured in a single unit including acylindrical body which covers the periphery of the above-mentionedinfrared sensor and a side part which covers at least a part of theabove-mentioned control board.

According to the present invention, the infrared sensor becomes less aptto undergo influences by the induction magnetic field from the inductionheating means, which occurs during the heating cooking. According to thepresent invention, it becomes possible to realize an induction heatingapparatus in which the heat generation of the infrared sensor itself dueto the influence of the magnetic field of the induction-heating coil issuppressed.

According to the present invention, stabilization of the ambienttemperature in the vicinity of the infrared sensor can be improved witha non-magnetic cylindrical body. Therefore, correct temperaturedetection becomes possible, and an induction heating apparatus capableof performing a stable heating control can be realized.

In the present invention, at least a part of the control board iscovered with the side part of the magneto-shielding member; therefore,an induction heating apparatus, in which the stable temperaturedetection by an infrared sensor can be performed without any influenceof leakage magnetic flux onto the control board from the inductionheating coil, can be realized.

In the present invention, by making the cylindrical body and the sidepart of magneto-shielding material to be a single unitary body, a goodassembling workability is realized. Thereby the accuracy of mountingpositions of the infrared sensor and the magneto-shielding member can beimproved. According to the present invention, an induction heatingapparatus having a high dimensional accuracy, including a fewer numberof parts, and also having an excellent assembling workability can berealized.

In the above-mentioned induction heating apparatus according to anotheraspect of the present invention, the above-mentioned cylindrical body ismade to be a nearly coaxial shape and is formed to be a doublecylindrical body.

According to the present invention, the magneto-shielding effectpreventing the leakage of magnetic flux onto the infrared sensor can beraised further, and at the same time, because of the increase of thethermal capacity of the magneto-shielding member, ambient temperaturearound the infrared sensor can be maintained more stably. According tothe present invention, an induction heating apparatus in which highlyaccurate temperature detection is attainable can be realized.

The above-mentioned induction heating apparatus according to anotheraspect of the present invention has openings at the joint part of theabove-mentioned cylindrical body placed inside and the above-mentionedcylindrical body placed outside.

In the present invention, even when the outside cylindrical body isheated, by cutting the heat at the openings, the thermal conduction tothe inside cylindrical body is reduced, thereby a substantial rise ofthe ambient temperature around the infrared sensor is prevented.According to the present invention, an induction heating apparatus inwhich the stable temperature detection is performed can be realized.

In the above-mentioned induction heating apparatus according to stillanother aspect of the present invention, material of the above-mentionedmagneto-shielding member is aluminum. As for aluminum, the reflectivityfor the infrared radiation is high (it transfers the infrared radiationradiated from the cooking container to be heated to the infrared sensorwith low loss), while infrared radiation from aluminum itself is little(SIN ratio (signal-to-noise ratio) of the infrared radiation radiatedfrom the cooking container to be heated is less apt to be degraded.).According to the present invention, an induction heating apparatus inwhich the temperature detection is performed in high accuracy can berealized.

In the above-mentioned induction heating apparatus according to stillanother aspect of the present invention, the above-mentionedmagneto-shielding member is made of die-cast, and the inside of theabove-mentioned cylindrical body is formed by the mirror-surfacefinishing. According to the present invention, an induction heatingapparatus in which the infrared radiation is detected correctly can berealized.

Owing to the above, a magneto-shielding member having a complicatedshape can be formed in a precise accuracy. To get a sufficientmagneto-shielding effect, it is desirable that the magneto-shieldingmember is to be thick enough to a certain degree. The magneto-shieldingmember can be formed at the optimum thickness with the die-cast. Theinner surface of the cylindrical body of die-cast can be formed by themirror-surface finishing. With this, the infrared radiation radiatedfrom the cooking container to be heated can be transferred to theinfrared sensor in low loss.

When the cylindrical body is double, it is sufficient to mirror-surfacefinish the inner surface of the inner side cylindrical body.

In the above-mentioned induction heating apparatus according to stillanother aspect of the present invention, the inner surface of theabove-mentioned cylindrical body is formed by the mirror-surfacefinishing with the roller burnishing.

The inside surface of the cylindrical body of the induction heatingapparatus of the present invention has a high reflectivity. With this,the infrared radiation radiated from the cooking container to be heatedcan be transferred to the infrared sensor with low loss. According tothe present invention, an induction heating apparatus in which theinfrared radiation is detected correctly can be realized.

In the above-mentioned induction heating apparatus according to stillanother aspect of the present invention, the distance between the uppersurface of the above-mentioned top plate and the upper surface of theabove-mentioned infrared sensor is in a range of 15 millimeters to 35millimeters.

When the distance from the top plate of the infrared sensor is tooclose, the infrared sensor undergoes the influence by the leakagemagnetic flux from the induction heating means and becomes too hot. Whenthe distance from the top plate is too far, input from the radiation ofthe cooking container to be heated becomes small. Consequently, thedistance between the upper surface of the top plate and the uppersurface of the infrared sensor is set to be in a range of 15 millimetersto 35 millimeters. In this range, the infrared sensor is less apt toundergo the influence by the leakage magnetic flux from the inductionheating means and moreover it can accept an enough amount of infraredradiation. Desirably, the distance between the upper surface of the topplate and the upper surface of the infrared sensor is set to be 26millimeters.

In the above-mentioned induction heating apparatus according to stillanother aspect of the present invention, thickness of theabove-mentioned magneto-shielding member is in a range of 1.5millimeters to 5 millimeters.

When the thickness of the magneto-shielding is too thin, the magneticshielding effect thereof becomes too weak, whereas when the thickness ofthe magneto-shielding member becomes too thick, casting defects areproduced inside the assembly after the casting and the magneticshielding effect diminishes. Therefore, the magneto-shielding member isformed uniformly in a range of thickness of 1.5 millimeters to 5millimeters. Desirably, a standard thickness of the magneto-shieldingmember is set to be 2 millimeters.

The above-mentioned induction heating apparatus according to stillanother aspect of the present invention further has a shield plate whichcovers almost all of the lower part of the above-mentioned controlboard.

Thereby, magnetic flux turning around from the underside of the controlboard is shielded out and the influence thereof can be prevented.According to the present invention, an induction heating apparatus thatis less apt to undergo the influence of the leakage magnetic flux can berealized.

In the above-mentioned induction heating apparatus according to stillanother aspect of the present invention, the above-mentionedmagneto-shielding member is grounded. According to the presentinvention, an induction heating apparatus that is still lesser apt toundergo the influence of the leakage magnetic flux can be realized.

In the above-mentioned induction heating apparatus according to stillanother aspect of the present invention, the above-mentionedmagneto-shielding member and the above-mentioned shield plate aregrounded. According to the present invention, an induction heatingapparatus that is still lesser apt to undergo the influence of theleakage magnetic flux can be realized.

The above-mentioned induction heating apparatus according to stillanother aspect of the present invention further has a first resin coverwhich holds the above-mentioned magneto-shielding member, theabove-mentioned first resin cover and the above-mentionedmagneto-shielding member compose a nearly closed space in which theabove-mentioned infrared sensor and the above-mentioned control boardare stored.

The above-mentioned induction heating apparatus according to stillanother aspect of the present invention further has a first resin coverwhich holds the above-mentioned magneto-shielding member and theabove-mentioned shield plate, the above-mentioned first resin cover, theabove-mentioned magneto-shielding member and the above-mentioned shieldplate compose a nearly closed space in which the above-mentionedinfrared sensor and the above-mentioned control board are stored.

The induction heating apparatus typically has a fan in the lower part ofthe main frame, and the fan is suppressing the heating of the inductionheating means by means of sending cooling wind to the induction heatingmeans. However, when this wind passes through the neighborhood of theinfrared sensor, the ambient temperature around the infrared sensorbecomes unstable, and therefore the accuracy of temperature detection ofthe cooking container to be heated by the infrared sensor is degraded.In the present invention, the resin cover and the magneto-shieldingmember compose a nearly closed space, and an infrared sensor and acontrol board are stored in it; with this configuration, the structureis such that no cooling wind blows through the above-mentioned nearlyclosed space. The present invention thus can realize an inductionheating apparatus in which the ambient temperature around the infraredsensor and the control board is kept constant, thereby the temperatureof the cooking container to be heated is detected in high accuracy.

In The above-mentioned induction heating apparatus according to stillanother aspect of the present invention further has a second resin coverwhich is placed between said infrared sensor and the circuit board onwhich the infrared sensor is installed, and which shields almost wholepart of the circuit board from the infrared radiation radiated from saidcooking container to be heated. Thereby it is possible to prevent thetime-lapsing degradation of the circuit board due to the infraredradiation radiated from the cooking container to be heated.

In the above-mentioned induction heating apparatus according to stillanother aspect of the present invention, the above-mentioned secondresin cover holds the above-mentioned infrared sensor in position of aspecified height from the above-mentioned circuit board. Owing to thatthe second resin cover holds stably the infrared sensor in the positionof the specified height from the circuit board, the infrared sensor canbe arranged at a certain upper position from the base plane of thecylindrical body of the magnetic material part. Thereby the infraredradiation radiated from the cooking container to be heated can betransferred to the infrared sensor with further lower loss.

The above-mentioned induction heating apparatus according to stillanother aspect of the present invention further has a second resin coverhaving a holding plane on which said infrared sensor is placed, and saidmagneto-shielding member has a recessed portion which is opened towardthe lower direction, said holding plane is positioned in said recessedportion, and the side planes and the base plane of a space defined bysaid second resin cover and said recessed portion is nearly closed.

According to the present invention, flow of wind of the cooling fan orair flowing around the infrared sensor can be prevented further.According to the present invention, by making the ambient temperature ofthe infrared sensor more constant, an induction heating apparatus inwhich the temperature of the cooking container to be heated is detectedin high accuracy can be realized.

In the above-mentioned induction heating apparatus according to stillanother aspect of the present invention, the above-mentioned infraredsensor is arranged in the central part of the above-mentioned inductionheating means provided in a spiral shape and ferrites are providedbetween the above-mentioned induction heating means and theabove-mentioned infrared sensor.

By providing the ferrites, it becomes possible to prevent an adverseeffect on the infrared sensor given by the magnetic flux issued from theinduction heating means. According to the present invention, aninduction heating apparatus in which the temperature of the cookingcontainer to be heated is detected in high accuracy can be realized.

Hereinafter, examples of embodiment showing the best mode forimplementing the present invention are specifically described with thedrawing.

Embodiment 1

The induction heating apparatus of the embodiment 1 of the presentinvention is described using FIG. 1, FIG. 4 and FIG. 6. FIG. 6 is asectional view showing the outline configuration of the inductionheating apparatus of the embodiment 1 of the present invention. FIG. 6was described in the example of prior art. FIG. 1 is a sectional view ofthe principal part showing the configuration of the induction heatingapparatus of the embodiment 1 of the present invention. FIG. 4 is anoutline drawing of exploded perspective view of the control unit of theembodiment 1 of the present invention. In FIG. 1, FIG. 4, and FIG. 6,numeral 1 is a main frame composing an outer casing of the inductionheating apparatus. The upper side plane of a main frame 1 is composed ofa top plate 2. The top plate 2 has a loading part 3 on which a cookingcontainer is placed. An induction heating coil (induction heating means)4 is provided in the lower part of the loading part 3 of the top plate2. The induction heating coil 4 induction-heats a cooking container 53(cooking container to be heated, not shown in FIG. 1).

Numeral 5 is an infrared sensor. The infrared sensor 5 detects theinfrared radiation radiated from the base plane of the cooking containerthrough the top plate 2 and outputs a signal according to thetemperature. The infrared sensor 5 is arranged at a position of 15millimeters to 35 millimeters under the upper surface of the top plate2. Desirably, it is 26 millimeters.

Numeral 6 is the magneto-shielding member that restrains the magneticflux leakage from induction heating coil 4 that is occurring during theinduction heating. In the embodiment 1, magneto-shielding member 6 ismade of die-cast of aluminum, and inner surface of a cylindrical body 6a is finished by the mirror-surface finishing (mirror-finished) byroller burnishing. Thickness of the magneto-shielding member 6 is 1.5millimeters to 5 millimeters. Desirably the thickness is 2 millimeters.The reflectivity of aluminum onto the infrared sensor 5 is high(infrared radiation radiated from the cooking container 53 istransferred to the infrared sensor 5 with low loss), and infraredradiation from the aluminum itself is little (SIN ratio (signal-to-noiseratio) of the infrared radiation radiated from the cooking container 53is less apt to be degraded.). The magneto-shielding member 6 has thecylindrical body 6 a. By making the structure to be that the cylindricalbody 6 a is made to be single unitary body with respect to themagneto-shielding member 6, the location accuracy between the infraredsensor 5 and the cylindrical body 6 a rises. The cylindrical body 6 atransfers the infrared radiation radiated from the cooking container 53to the infrared sensor 5 with low loss and also prevents that themagnetic flux from induction heating coil 4 leaks to the infrared sensor5. The magneto-shielding member 6 covers the infrared sensor 5 and acontrol board 7 so that it stabilizes the ambient temperature around theinfrared sensor 5 and a control board 7.

Numeral 7 is the control board. The control board 7 controls the outputof the induction heating coil 4. Specifically, a temperature calculationmeans 51 and a control means 52 are provided on the control board 7. Thetemperature calculation means 51 calculates the temperature of thecooking container 53 based on the output signal of infrared sensor 5.The control means 52 controls the power supply to the induction heatingcoil 4 based on the information obtained from the temperaturecalculation means 51.

Numeral 8 is a shield plate. The shield plate 8 covers almost all thelower part of control board 7. The shield plate 8 shields the magneticflux turning from the underside of the control board and prevents theinfluence thereof. The magneto-shielding member 6 and the shield plate 8are grounded with screws 12 b.

Numeral 9 is a first resin cover. The first resin cover 9 holdsmagneto-shielding member 6 and shield plate 8. The first resin cover 9and the magneto-shielding member 6 are joined by screws 12 a, 12 b, and12 c, forming a nearly closed space in which the infrared sensor 5, thecontrol board 7, and the shield plate 8 are stored (called as “controlunit”). The induction heating apparatus has a fan (not shown) in thelower part of the main frame, and the fan suppresses the heating of theinduction heating coil 4 by means of sending cooling wind to theinduction heating coil 4. The nearly closed space composed of the firstresin cover 9 and the magneto-shielding member 6 prevents a flow ofcooling wind flowing through the neighborhood of the infrared sensor 5from the lower part. Thereby the ambient temperature in the vicinity ofthe infrared sensor 5 is stabilized and hence a high accuracy detectionof temperature is realized.

In place of the above, it is also possible that the base plane of thefirst resin cover 9 is opened toward the lower direction and the shieldplate 8 blocks this base plane. In this case, the first resin cover 9,shield plate 8 and magneto-shielding member 6 compose a nearly closedspace and the infrared sensor 5 and the control board 7 are stored init.

A second resin cover 13 is provided on the control board 7 (circuitboard). The second resin cover 13 holds the infrared sensor 5 in theposition with a fixed height from the control board 7. The second resincover 13 is arranged between the infrared sensor 5 and the control board7, on which the infrared sensor is installed, and shields almost all ofthe control board 7 from the infrared radiation radiated from thecooking container 53. Terminals of the infrared sensor 5 are directlysoldered to the control board 7. The second resin cover 13 has a holdingplane 13 a on which the infrared sensor 5 is placed, and themagneto-shielding member 6 has a recessed portion 6 b which is openedtoward the lower direction; and the holding plane 13 a is positionedinside the recessed portion 6 b, and the side planes and the base planeof a space defined by the second resin cover 13 and the recessed portion6 b are closed nearly completely. By this configuration, it is possibleto prevent further that wind of the cooling fan or air flows around theinfrared sensor. The ambient temperature of the infrared sensor 5 iskept constant further, thereby temperature of the cooking container 53can be detected in high accuracy.

Numerals 10 and 11 are ferrites having the magneto-shielding effect.Ferrite 10 is arranged between the induction heating coil 4 and theinfrared sensor 5 as well as on a circle having its center on a verticalaxis running through the infrared sensor 5. Top surface of the ferrite10 is set higher than the upper side surface of the induction heatingcoil 4; and the underside of ferrite 10 extends to the lower directionso that a line connecting the outermost periphery of the inductionheating coil 4 and the infrared sensor 5 is blocked by the ferrite. Theferrites 11 are arranged in the radial direction.

With the above configuration, the infrared sensor 5 becomes less apt tobe influenced by the induced magnetic field from the induction heatingcoil 4 that is occurring during the cooking by the induction heating.Since the heat generation of the infrared sensor 5 itself caused by theleakage magnetic flux is suppressed, correct temperature detection canbe performed and thereby a stable heating control can be realized.

Embodiment 2

Using FIG. 3 and FIG. 6, the induction heating apparatus of anembodiment 2 of the present invention is described. FIG. 6 is across-sectional drawing showing the outline configuration of theembodiment 2 of the present invention. FIG. 2 is a cross-sectionaldrawing of main part showing the configuration in an embodiment 2 of thepresent invention. An induction heating apparatus of the embodiment 2differs from the embodiment 1 in the cylindrical body ofmagneto-shielding member 21. Since the other configuration than that isidentical with embodiment 1, identical numerals are used for theidentical components and explanations thereof are omitted.

The magneto-shielding member 21 of the embodiment 2 is described. Themagneto-shielding member 21 has double cylindrical bodies 21 a and 21 b,which are approximately coaxial to each other. By making the cylindricalbody to be a double configuration, the magneto-shielding effect withrespect to the infrared sensor 5 is raised, and moreover, by an increaseof thermal capacity owing to the double configuration, the ambienttemperature in the vicinity of the infrared sensor 5 as well as thecontrol board 7 can be maintained further stably. The induction heatingapparatus of the embodiment 2 can detect the temperature in furtherhigher accuracy.

By making the structure to be that the cylindrical bodies 21 a and 21 bare made as a single unitary body, a uniform space (having an insulationeffect) can be secured between the cylindrical bodies 21 a and 21 b,thereby the ambient temperature in the vicinity of the infrared sensor 5can be stabilized remarkably. Moreover, owing to an increase in accuracyof the position of the infrared sensor 5 and the magneto-shieldingmember 21, the temperature detection can be performed more accurately,thereby a stable heating control can be achieved.

Embodiment 3

Using FIG. 3 and FIG. 6, the induction heating apparatus of anembodiment 3 of the present invention is described. FIG. 6 is across-sectional drawing showing the outline configuration of a positionof the embodiment 3 of the present invention. FIG. 3 is across-sectional drawing of principal part showing the configuration inan embodiment 3 of the present invention. An induction heating apparatusof the embodiment 3 differs from the embodiment 2 in that themagneto-shielding member 31 has openings 32. Since the otherconfiguration than that is identical with embodiment 2, identicalnumerals are used for the identical components and explanations thereofare omitted.

The magneto-shielding member 31 of the embodiment 3 is described. Themagneto-shielding member 31 has the openings 32 between the doublecylindrical bodies 31 a and 31 b that are almost coaxial to each other.In the embodiment 3, number of openings is four. Even when thecylindrical body 31 b generates heat, by cutting the heat by theopenings 32, the thermal conduction to the cylindrical body 31 a can bereduced further. Therefore, the ambient temperature in the vicinity ofthe infrared sensor 5 can be stabilized.

According to the present invention, the influence of the leakagemagnetic flux from the induction heating means is avoided by coveringthe periphery of the infrared sensor and at least a part of the controlboard with the magneto-shielding member; therefore, the inductionheating apparatus in which the infrared sensor performs stabletemperature detection can be realized.

In the present invention, by making the cylindrical body and the sidepart of the magneto-shielding member to be a single unitary body, a goodassembling workability is realized. According to the present invention,an induction heating apparatus having a high dimensional accuracy, afewer numbers of parts, and also having an excellent assemblingworkability can be realized.

In the present invention, the cylindrical body is formed in a nearlycoaxial structure of double configuration; with this structure, themagneto-shielding effect to prevent the leakage of magnetic flux ontothe infrared sensor 5 is raised further, and moreover, by an increase ofthe thermal capacity owing to the placement of the magneto-shieldingmember, the ambient temperature in the vicinity of the infrared sensor 5can be maintained further stably. According to the present invention, anadvantageous effect that an induction heating apparatus in which thetemperature detection is performed in a further higher accuracy can berealized.

By making the configuration in a manner that the openings are providedat the joint part of outside and inside of the double cylindrical body,the following effects develop: Even if the outside of the cylindricalbody is heated, the thermal resistance up to the center at which theinfrared sensor is placed becomes larger; therefore, the rapid change ofthe ambient temperature in the vicinity of the infrared sensor can beavoided. Moreover, according to the present invention, an advantageouseffect that an induction heating apparatus in which the further stabletemperature detection is performed can be realized.

Although the present invention has been described with respect to itspreferred embodiments in some detail, the disclosed contents of thepreferred embodiments may change in the details of the structurethereof, and any changes in the combination and sequence of thecomponents may be attained without departing from the spirit and scopeof the claimed invention.

INDUSTRIAL APPLICABILITY

The present invention is useful for the induction heating apparatusequipped with the infrared sensor or the like.

1. An induction heating apparatus characterized in that it has; a mainframe composing an outer casing, a top plate provided on the upper sidesurface of said main frame and having at least one loading part on whicha cooking container to be heated is placed, an induction heating meanswhich is provided in the lower part of said loading part and is to heatsaid cooking container to be heated, an infrared sensor which isprovided in the neighborhood of said induction-heating means andreceives the infrared radiation radiated from said cooking container tobe heated, and outputs the detected signal corresponding to the amountof the infrared radiation, a control board that detects the temperatureof said cooking container to be heated based on said detected signal,and controls the output of said induction heating means, amagneto-shielding member configured in a single unitary body including acylindrical part which covers the periphery of said infrared sensor anda side part which covers at least a part of said control board.
 2. Aninduction heating apparatus of claim 1 characterized in that saidcylindrical body is formed in a nearly coaxial structure of doubleconfiguration.
 3. An induction heating apparatus of claim 2characterized in that it has openings at a joint part of saidcylindrical body positioned inside and said cylindrical body positionedoutside.
 4. An induction heating apparatus of claim 1 characterized inthat the material of said magneto-shielding member is aluminum.
 5. Aninduction heating apparatus of claim 1 characterized in that saidmagneto-shielding member is made of die-cast, and its inner surface isformed by the mirror-surface finishing.
 6. An induction heatingapparatus of claim 5 characterized in that the inner surface of saidcylindrical body is finished as the mirror-surface by the rollerburnishing.
 7. An induction heating apparatus of claim 1 characterizedin that the distance between the upper side surface of said top plateand the upper side surface of said infrared sensor is in a range of 15mm to 35 mm.
 8. An induction heating apparatus of claim 1 characterizedin that the thickness of said magneto-shielding member is in a range of1.5 mm to 5 mm.
 9. An induction heating apparatus of claim 1characterized in that it further has a shield plate that covers nearlywhole lower part of said control board.
 10. An induction heatingapparatus of claim 9 characterized in that said magneto-shielding memberand said shield plate are grounded.
 11. An induction heating apparatusof claim 9 characterized in that it further has a first resin coverwhich holds said magneto-shielding member and said shield plate, andsaid first resin cover, said magneto-shielding member and said shieldplate compose a nearly closed space in which said infrared sensor andsaid control board are stored.
 12. An induction heating apparatus ofclaim 11 characterized in that it further has a second resin coverhaving a holding plane on which said infrared sensor is placed, and saidmagneto-shielding member having a recessed portion which is openedtoward the lower direction, said holding plane is positioned in saidrecessed portion, and the side planes and the base plane of a spacedefined by said second resin cover and said recessed portion is nearlyclosed.
 13. An induction heating apparatus of claim 1 characterized inthat said magneto-shielding member is grounded.
 14. An induction heatingapparatus of claim 1 characterized in that it further has a first resincover which holds said magneto-shielding member, and said first resincover and said magneto-shielding member compose a nearly closed space inwhich said infrared sensor and said control board are stored.
 15. Aninduction heating apparatus of claim 14 characterized in that it furtherhas a second resin cover having a holding plane on which said infraredsensor is placed, and said magneto-shielding member has a recessedportion which is opened toward the lower direction, said holding planeis positioned in said recessed portion, and the side planes and the baseplane of a space defined by said second resin cover and said recessedportion is nearly closed.
 16. An induction heating apparatus of claim 1characterized in that it further has a second resin cover which isplaced between said infrared sensor and the circuit board on which theinfrared sensor is installed, and which shields almost whole part of thecircuit board from the infrared radiation radiated from said cookingcontainer to be heated.
 17. An induction heating apparatus of claim 16characterized in that said second resin cover holds said infrared sensorat a position of a specified height from said circuit board.
 18. Aninduction heating apparatus of claim 1 characterized in that saidinfrared sensor is placed at the central part of said induction heatingmeans which is arranged spirally, and ferrites are provided between saidinduction heating means and said infrared sensor.